Numerical investigation of flow and heat transfer characteristics in plate-type fuel channels of IAEA MTR based on OpenFOAM

Due to the independence of coolant channels, the occurrence of channel blockage will affect the flow and heat transfer characteristics of plate-type fuel assembly significantly, which may lead to coolant boiling and threaten the structural integrity of reactor core. In this work, based on open source platform OpenFOAM, the wall boiling model under two fluid framework was established, and the validation was performed against the subcooled boiling experiment conducted by Bartolemei et al. After that, a typical structure with four parallel coolant channels were modeled, and two kinds of flow blockage conditions, including the thin-wall blockage and plate-bending blockage conditions, were performed to investigate the influence of blockage on the flow and heat transfer features. Simulation results show that the proportion of mass flow rate decreases significantly with the value of 7.82% and 10.06% and the outlet temperature increases correspondingly to the value of 326.69K and 325.81K in blocked coolant channels under the thin-wall blockage and plate-blending blockage conditions respectively. Subcooled boiling occurs at the end of blocked channel under the high power level, and the coolant returns to the subcooled state after mixing in the upper chamber. The thin-walled blockage causes sudden change of the channel shape, leading to the flow stagnation zone and weak zone accompanied by the local liquid temperature rise.